In the process of investigating, one of the matters I have difficulty reconciling is the Christian belief that the Messiah is equivalent to the Son of G-d. Nowhere in the Masoretic text (perhaps more so in the Septuagint) of the Hebrew Bible have I found evidence that the Messiah is supposed to be divine.

Another challenge for me is that Jesus did not fulfill the prophecies that the Messiah is supposed to fulfill. These include world peace between the nations, the rebuilding of the Temple, and the observance of Torah Law on a worldwide basis.

Jesus does fulfill these prophecies, but not through the temporal order. The Temple He builds is not made of stone, but people. The peace He gives is not an end to war but an end to sin, sin being the cause of war and death in general. The Law He gives is not the Levitical external observances (which, like the temporal Davidic kingdom, is temporary) but that which is to be written on the hearts of all.

We know that some time must pass between the two because the nations (i.e. the Gentiles) are given time to inquire as to the truth before they are judged. How much time that is will not be revealed to us.

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And finally, the concept of a Savior, a Redeemer of the sins of humanity, runs counter to the Hebrew Bible's prohibition against vicarious atonement.

The Levitical priesthood is entirely based on vicarious atonement; Aaron and his successors offered the sacrifices for the atonement of all of Israel, see e.g. Lev. 19:22.

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Even more problematic, it is not a concept associated with the Messiah. Moses reiterates that atonement is a continual process and not so difficult to achieve by one's own efforts in following the Law, however imperfectly.

I just cannot see the High Priest putting his hand on the scapegoat and recounting every single sin of every single Israelite for the past year (Lev. 16:21). Yom Kippur would be over long before he was anywhere near done. The scapegoat ritual, the purification rite of the red heifer, the Passover sacrifice, and many other Levitical rituals were impossible to fulfill perfectly because the victims offered were always imperfect (the slightest blemish or bent hair disqualified the ram, heifer, etc.) or the sins of Israel were just too numerous. The point of the Mosaic Law was to demonstrate to men the distance between man and G-d could not be bridged except from G-d's side. Even if G-d gave man the tools with which to address his sinfulness, man would still fail. That is why the work of salvation would have to be accomplished by G-d.

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IOW, the notion of universal redemption and salvation from original sin is foreign to Judaism.

It wasn't foreign to the Tanakh.

Starting at the beginning, we see the serpent in the Garden of Eden, who causes humanity to begin to sin. G-d's response is to promise universal redemption by promising to act in such a way that will put enmity between a Woman and Her Offspring and the serpent, and that through them, the serpent will be destroyed although the Offspring will be wounded (i.e. the crucifixion):

The Woman in question cannot be Eve, because Eve's disobedience is what caused sin to enter into the world; Eve was clearly not at enmity with the serpent. The Woman is someone to come in the future.

In the Book of Job, the serpent is shown to be not a generalized concept of evil, but an individual: a fallen angel, an accuser and slanderer, an adversary ("satan" from the Hebrew, literally ‘adversary’) of humanity.

And the Psalms make clear that the original disobedience of man has caused the sin of Adam to enter into every person (excepting only the Woman through whom the original Gen. 3:15 promise would be fulfilled).
Psalm 51:3-5 (NRSV)

3 For I know my transgressions,
and my sin is ever before me.
4 Against you, you alone, have I sinned,
and done what is evil in your sight,
so that you are justified in your sentence
and blameless when you pass judgement.
5 Indeed, I was born guilty,
a sinner when my mother conceived me.

The New Covenant established by Jesus Christ is the fulfillment of the original Genesis 3:15 promise. The Woman is the Blessed Virgin Mary; Her Offspring is Jesus Christ, Immanuel, Mighty God. The serpent's head is crushed at Calvary (the 'place of the skull').